This invention generally relates to techniques for operating and controlling an optical switch system. More particularly, the present invention provides a method for operating and controlling movement of a micro-mirror structure coupled to a pair of torsion bars in a transparent manner. Merely by way of example, the present invention is implemented on a micro-mirror assembly for switching an optical signal, but it would be recognized that the invention has a much broader range of applicability. The mirror can be used in a switching device for long haul communications. The invention can be applied to other types of networks including local area networks, enterprise networks, small switch designs (e.g., two by two) and the like.
As the need for faster communication networks becomes more desirable, digital telephone has progressed. Conventional analog voice telephone signals have been converted into digital signals. These signals can be 24,000 bits/second and greater in some applications. Other telephone circuits interleave these bit streams from 24 digitized phone lines into a single sequence of 1.5 Mbit/second, commonly called the T1 or DS1 rate. The T1 rate feeds into higher rates such as T2 and T3. A T4 may also be used. Single mode optical fibers have also been used at much higher speeds of data transfer. Here, optical switching networks have also been improved. An example of such optical switching standard is called the Synchronous Optical Network (SONET), which is a packet switching standard designed for telecommunications to use transmission capacity more efficiently than the conventional digital telephone hierarchy, which was noted above. SONET organizes data into 810-byte xe2x80x9cframesxe2x80x9d that include data on signal routing and designation as well as the signal itself. The frames can be switched individually without breaking the signal up into its components, but still require conventional switching devices.
Most of the conventional switching devices require the need to convert optical signals from a first source into electric signals for switching such optical signals over a communication network. Once the electric signals have been switched, they are converted back into optical signals for transmission over the network. As merely an example, a product called the SN 16000 is BroadLeaf(trademark) Network Operating System (NOS) made by Sycamore Networks, Inc. uses such electrical switching technique. Numerous limitations exist with such conventional electrical switching technique. For example, such electrical switching often requires a lot of complex electronic devices, which make the device difficult to scale. Additionally, such electronic devices become prone to failure, thereby influencing a reliability of the network. The switch is also slow and is only as fast as the electrical devices. Accordingly, techniques for switching optical signals using a purely optical technology have been proposed. Such technology can use a wave guide approach for switching optical signals. Unfortunately, such technology has been difficult to scale for switching a high number of signals from a bundle of optical fibers, which may be desirable today. Other companies have also been attempting to develop technologies for switching such high number of signals, but have been unsuccessful. Such switches are also difficult to manufacture effectively and reliably. Other examples of optical switching networks include access, metropolitan and Dense Wavelength Division Multiplexing (DWDM) networks.
As merely an example, some companies have been attempting to use mirrors to switch an optical beam from one fiber to another. The use of mirrors in telecommunication signals has some advantages such as low signal loss and the like. Such mirrors, however, are often difficult to manufacture in a high density mirror array. In particular, such mirrors are often fragile and prone to damage during fabrication. U.S. Pat. No. 5,969,465, assigned to XROS, Inc. describes such a mirror, which is often difficult to make and operate high density array structures. Such mirrors can often only operate in a linear region through electrostatic force. Such linear region generally provides a limited amount of movement of the mirror through a spatial region, which limits its switching effectiveness. Accordingly, it is often difficult to use such a mirror design to operate high density arrays.
From the above, it is seen that an improved way for operating movement of a mirror assembly for switching a signal is highly desirable.
According to the present invention, a technique including a method and apparatus for operating and controlling a switch system is provided. More particularly, the present invention provides a method for operating and controlling movement of a micro-mirror structure coupled to a pair of torsion bars in a transparent manner. Merely by way of example, the present invention is implemented on a micro-mirror assembly for switching an optical signal, but it would be recognized that the invention has a much broader range of applicability. The mirror can be used in a switching device for long haul communications. The invention can be applied to other types of networks including local area networks, enterprise networks, small switch designs (e.g., two by two) and the like.
In a specific embodiment, the invention provides a method for switching signals using one of a plurality of mirrors in an array structure. The method includes determining an optical path to be formed between an input fiber and an output fiber. method also includes determining a set of mirrors to be used to form the optical path. The set of mirrors includes at least a first mirror. The first mirror is coupled to a mechanical spring assembly and an actuation assembly. The method captures an analog signal indicative of a spatial position of the first mirror using a position sensing device. The sensing device is coupled to the mirror. The method also converts the signal analog signal into a digital signal. The method processes the digital signal indicative of the spatial position of the mirror using the digital signal processing device to obtain a characteristic of the mirror. The method provides a control signal based upon the characteristic of the mirror. The converts the control signal into an analog control signal. The method uses the analog control signal with the actuation assembly to set a desired position of the first mirror.
In an alternative specific embodiment, the invention provides a system for controlling and switching optical signals using selection of optical paths from a first fiber bundle to a second fiber bundle in a transparent manner. The system has a client device including a graphical user interface for input of switching information by a user. The client device is substantially free from interaction by the user to optimize an optical path. A network is coupled to the client device for receiving the switching information. A switch control apparatus is coupled to the network and a switch device is coupled to the switch control apparatus. The switch device has a fiber input device and a set of mirrors from a plurality of mirrors coupled to the fiber input device. The set of mirrors include at least a first mirror that is capable of being moved about a mechanical spring. The first mirror is coupled to the mechanical spring device to form a counter-acting force to the mirror in a first direction. A sensing is device coupled to the first mirror. The sensing device is adapted to capture position information from the first mirror. An analog to digital converter device is coupled to the sensing device. Such digital to analog converter device converts the position information into a digital signal. A signal processing device is coupled to the analog to digital converter. The digital signal processing device processes the digital signal to derive a digital control signal based upon a characteristic of the first mirror device. The device also has a digital to analog converter device coupled to the signal processing device. The digital to analog converter device is adapted to convert the digital control signal to an analog control signal. The device has an actuation device coupled to the first mirror and coupled to the digital to analog converter. The actuation device receives a signal derived from the analog control signal to drive the mirror about the mechanical spring using the analog control signal to set a desired position of the first mirror.
Many benefits are achieved by way of the present invention over conventional techniques. For example, the present technique provides an easy to use process that relies upon conventional technology. The present invention provides a novel way of controlling and operating a MOEMS, which can include a micro-mirror assembly. In one aspect, the invention allows for high scale integration of mirror devices to form high density and performance switching devices. Such switching device can include more than 10 (ten) mirror elements. In some embodiments, such switching devices can include more than 200 (two hundred) or even thousands (one thousand to four thousand and greater) mirror elements for switching respective signals for optical switching applications. The invention also provides for a stable switch position during operation for a MOEMS, which may be subjected to internal and/or external noise from a mechanical (e.g., vibration, shock), thermal, gravitational or electrical force or forces. Such forces can be detrimental to precise switching requirements of the MOEMS for optical switching applications in the telephone industry. The present feed back control can also provide for stable operation that may be related to drift caused by electrical, mechanical, and/or thermal. The invention can also take into account degradations over a lifetime of a switching device, which may be prone to fatigue or the like. In preferred embodiments, the present system has stable operating performance (e.g., low bit error rates, low dB losses, low insertion losses) due to the feed back process. The present control system can be used to reduce switching time (e.g., less than 20 milliseconds) as compared to conventional open loop configurations, which often oscillate and cannot find a stable position efficiently. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits will be described in more throughout the present specification and more particularly below.